Many known access control systems include an anti-pass back (APB) feature that prevents unauthorized users from tailgating an authorized user to gain access to a secured region. For example, when a user presents a valid access card to a card reader to gain access to a secured region, an APB feature prevents an unauthorized second user from using the same card to gain access to the region. Such APB features can include designating different card readers as an IN reader or an OUT reader and controlling access to the secured region in accordance with three rules: (1) a user presenting a valid card to an IN reader must present the same card to an OUT reader before again presenting the card to an IN reader, (2) after presenting a valid card to an IN reader, a user presenting the same card to the same or another IN reader, without presenting the card to an OUT reader, will be disallowed access, and (3) after presenting a valid card to an OUT reader, a user presenting the same card to the same or another OUT reader, without presenting the card to an IN reader, will be disallowed access.
FIG. 1 is a block diagram of a known access control system 100 that includes an APB feature. As seen in FIG. 1, the system 100 can include four sites S1, S2, S3, and S4. The system 100 can also include one host system 150 that supports and communicates with access controllers at each of the sites S1, S2, S3, and S4. For example, the host system 150 can be any computer or device that is capable of transmitting an APB status update to an access controller.
As seen in the exemplary system 100, Site 1 S1 can include 10 access controllers S1C1-S1C10, Site 2 S2 can include 5 access controllers S2C1-S2C5, Site 3 S3 can include 15 access controllers S3C1-S3C15, and Site 4 can include 30 access controllers S4C1-S4C30. Access controllers are known in the art. For example, as seen in FIG. 2, an access controller 210 can communicate with a plurality of card readers 220, a plurality of input devices 230, and a plurality of output devices 240.
When a valid card transaction occurs at a card reader in communication with one access controller, for example, access controller S1C1, the access controller S1C1 can transmit a corresponding triggering signal to the host system 150. It is to be understood that a triggering signal as used herein includes a signal transmitted from an access controller to a host system responsive to a valid card transaction occurring at a card reader in communication with the access controller. It is to be further understood that a valid card transaction is one that allows a user to gain access via a secured entryway by presenting a valid access card to a card reader. Upon receipt of the triggering signal from the access controller S1C1, the host system 150 can globally transmit or download an appropriate APB status update to all other access controllers in the system, including S1C2-S1C10, S2C1-S2C5, S3C1-S3C15, and S4C1-S4C30, so that each access controller can be updated for abiding by the APB rules described above.
However, large secured facilities and regions can include thousands of card readers in communication with many access controllers, and the number of times the host system transmits an APB status update is controlled by the following factors: (1) the number of valid card transactions at all card readers in a secured region, and (2) the number of access controllers following APB rules. For example, a higher number of valid card transactions will cause a higher number of APB status updates to be transmitted by a host system, and a higher number of access controllers following APB rules will cause a higher number of APB status updates to be transmitted by a host system for each valid card transaction. Chart 1 in FIG. 3 and Table 1 in FIG. 4 are illustrative of these principals.
Indeed, in known systems, Equation (1) is explanatory:Total number of APB status updates downloaded per second=(Total number of APB access controllers communicating with a host system−1)×Total number of valid card transactions per second  Equation (1)It is to be understood that the total number of APB access controllers communicating with the host system is subtracted by 1 because the APB status update is not transmitted to the access controller that transmitted the triggering signal.
In accordance with the above, in the exemplary known access control system 100 in FIG. 1 with 60 access controllers, a valid card transaction occurring at a card reader in communication with one access controller S1C1 can result in the host system 150 downloading an APB status update 59 times.
The known systems and methods described above have several disadvantages. For example, when a large number of APB status updates are downloaded, big backlogs on both the host system and the access controllers can be created. Such backlogs can create functional and operational issues that are undesirable. For example, when a user enters a secured area via a first IN card reader supported by a first access controller, the user will not be able to exit the secured area via a second OUT card reader supported by a second access controller if the host system does not download and the second access controller does not receive an appropriate APB status update in a timely manner. Similar issues can arise during an emergency evacuation of the secured area. Indeed, a user may not be able to leave a compromised secured area to reach a safe area in a timely manner.
To alleviate some of the functional and operational issues described above that are caused by performance and throughput constraints, some known systems and methods have reduced the number of APB access controllers supported by a single host system. However, any such reduction leads to higher costs in maintaining the hardware, software, and support of additional host systems that are required to accommodate and support a large number of APB access controllers.
In view of the above, there is a continuing, ongoing need for improved systems and methods.